The correct answer is C - carbon dioxide.
The distribution of gases in the earth's atmosphere is as follows:
1. Nitrogen - 78 %
2. Oxygen - 21 %
3. Argon - 0.93 %
4. Carbon dioxide - 0.038%
Nitrogen, oxygen and argon are permanent gases whose percentage in the atmosphere does not change from day to day.
Gases such as carbon dioxide, nitrous oxides, methane, and ozone are known as trace gases which make up 0.1% of the atmosphere.